1. Field of the Invention
This invention relates to a cooling control system for an internal combustion engine and more particularly to a total cooling control system employing an electric water pump, various temperature sensors, a radiator flow control valve, a radiator fan motor and a controller to control the cooling system to maintain an engine operating temperature within a narrow range around a target temperature.
2. Description of Related Art
Conventional internal combustion cooling systems generally employ a mechanical water pump which is operated based on engine speed, a thermostat, and a radiator to maintain the engine temperature within a safe operating temperature range. However, since the speed of the mechanical water pump is directly related to the engine rpm, at low engine rpm and high engine load, the speed of the mechanical water pump may limit the ability of the cooling system to dissipate the required heat from the engine. This condition can lead to the temperature of the engine exceeding the controllable range of the thermostat. In addition, at high engine rpm and low load conditions, the capacity of the water pump may exceed the necessary cooling requirements and energy may be wasted due to circulating excess fluid. This wasted energy represents a potential fuel savings.
With the conventional mechanical water pump and thermostat, generally the set point for the engine operating temperature is fixed. With a fixed operating temperature, the cooling system may not be tuned to optimize emission and power based on engine load.
Accordingly, a need exists to provide a total cooling control system to maintain the engine operating temperature within a narrow range around a target temperature with the engine target temperature and mass flow rate through the engine being a direct function of the he at released and an indirect function of engine load.